Wobble plate compressor

ABSTRACT

A wobble plate compressor ( 101 ) comprises at least one wobble plate ( 017 ) assigned at least two piston-cylinder assemblies. The wobble plate compressor ( 101 ) forms a multistage compressor in which the piston-cylinder assemblies are connected in series in the flow and the cubic capacity of the piston-cylinder assemblies is progressively reduced in series.

FIELD OF THE INVENTION

The present invention relates in general to compressors and, forexample, to a wobble plate compressor as well as to use of a wobbleplate compressor for compressing natural gas.

BACKGROUND OF THE INVENTION

Wobble plate machines are essentially piston machines in which thepiston(s) is/are not driven by a crank but by a swash or wobble plate,i.e. a plate skew seated on an axis which “wobbles” on rotation of theaxis, but not like a radial plate in which the points rotate in thevicinity of the edge, instead in a rotary plane inclined to the axis.Arranged opposite this wobble plate for each piston is a stationary conrod substantial parallel to the drive shaft and the con rod(s) areadvanced or retracted by the wobbling plate.

In practice such wobble plate machines are mainly employed as pumps(i.e. for pumping incompressible fluids, in other words liquids). Basicuse of the wobble plate design in pumps is known, for example, from theGerman “Dubbel” mechanical engineering text book, 17^(th) Edition,published by Springer-Verlag, 1990, pages H4-H8.

In addition, wobble plate machines also find use as compressors (i.e.compressors for compressible fluids, i.e. gases), particularly inrefrigerators. Thus wobble plate type refrigerant compressors are known,for example, from U.S. Pat. No. 4,008,005 as well as from EP 0 530 730A1. In these wobble plate machines the actual wobble plate isnon-rotatable but is controlled by a rotatable wobble member to producethe wobble motion. To compensate, at least in part, one disadvantage ofnon-compensated forces and moments general to wobble plate machines(substantially resulting from gas forces during compression and suddenrelaxation when the outlet valve is opened and the mass forces stemmingfrom the reciprocating pistons) it is proposed in the cited documents toarrange a plurality of (in this case, five or six) piston-cylinderassemblies regularly distributed circumferentially. The plurality ofcylinders is connected in parallel as regards the delivery of the gasflow to be compressed. It is generally the case that these known wobbleplate pumps have a relatively low compression ratio since a refrigerantis compressed generally to not more than 2 bar.

A further wobble plate type refrigerant compressor is known from EP 0599 642 A1 in which it is proposed to equip the piston-cylinderassemblies with piston rings of polytetrafluoroethylene (PTFE).

Known in conclusion are special types of wobble plate compressors inwhich the piston-cylinder assemblies extend not just to one side of thewobble plate but to both sides as it reads from U.S. Pat. No. 5,611,675(with a swash plate), DE patent 530 071 and FR patent 918.307 (with twowobble plates seated on a common shaft, inclined to each other).

SUMMARY DESCRIPTION OF THE INVENTION

The invention relates to a wobble plate compressor comprising at leastone wobble plate associated with at least two piston-cylinderassemblies. The wobble plate compressor forms a multistage compressor inwhich the piston-cylinder assemblies are connected in series in the flowand the cubic capacity of the piston-cylinder assemblies isprogressively reduced in series.

A further aspect relates to a method in which one such wobble platecompressor is used for compressing natural gas to a pressure of at least200 bar.

Another aspect relates to a wobble plate compressor comprising at leastone pair of wobble plates, each of which is associated with at least onepiston-cylinder assembly. Each of the two wobble plates is powered by adrive shaft stub, the two drive shaft stubs being arranged coaxiallycounter-rotating.

Further features read implicitly from the disclosed devices or areevident to the person skilled in the art from the following detaineddescription of embodiments and the attached drawing.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of the invention will now be described by way of examplewith reference to the attached drawing in which:

FIG. 1 is a full view of a dual wobble plate compressor shown in partiallongitudinal section;

FIG. 2 is a view of half of the dual wobble plate compressor as shown inFIG. 1 but here on a magnified scale; and

FIG. 3 is an illustration showing use of the compressor as shown inFIGS. 1 and 2 for compressing natural gas in fuelling a vehicle withcompressed natural gas (CNG).

DESCRIPTION OF THE PREFERRED EXAMPLE EMBODIMENTS

FIGS. 1 and 2 show by way of an example a wobble plate compressor.Before detaining FIGS. 1 and 2 the embodiments are firstly explained asfollows:

In some of the embodiments as described in the following a wobble platetype compressor is provided suitable for achieving a high overallcompression ratio. For this purpose the wobble plate compressor in someembodiments is configured as a multistage compressor in which aplurality of piston-cylinder assemblies is connected in series in theflow and the cubic capacity of the piston-cylinder assemblies isprogressively reduced in series. Multistage compressors are known (e.g.as it reads from the German “Dubbel” mechanical engineering text book,17^(th) Edition, published by Springer-Verlag, 1990, pages P23-P33);these known multistage compressors are all crankshaft type pistoncompressors, however.

In some of the embodiments the piston-cylinder assemblies connected inseries are interconnected in series by conduit and valve assemblies.

The multistage configuration achieves substantial final pressures: basedon atmospheric pressure and ignoring the effects of the gas being heatedand cooled and its friction loses, some embodiments are capable ofachieving, for example, with a compression ratio of roughly 1:4 percylinder, an increase in pressure of 16 bar and 256 bar in a two andfour cylinder series assembly respectively. However, the true pressuresattained are usually less, because of the effects ignored in the aboveachievements. In some embodiments forced cooling of the cylinders and/orof their interconnecting conduits is needed to achieve an effectiveintermediate cooling, e.g. by forced ventilation with ambient air orcooling by cooling water, etc. In other embodiments merely convectioncooling of the pistons and/or the conduits by ambient air is providedfor.

In some embodiments e.g. four piston-cylinder assemblies are assignedper wobble plate, whereas in other embodiments just two piston-cylinderassemblies are provided per wobble plate which, as such, is lessfavorable as regards force and moment compensation. But in a few ofthese embodiments—as detained further on below—a second wobble plate isprovided in a casing, powered counter-rotatively to the first wobbleplate and arranged together therewith in a common casing. The casing canthus absorb the forces and moments of the two wobble plate assemblies inpartly compensating them counterwise, since due to the counter rotativearrangement they are employed opposite in sign at least in part.

When again assuming the gas is not heated in compression, it neitherbeing cooled nor any friction loses existing, then—because ofmaintaining the mass flow of the compressed gas—the seriespiston-cylinder assemblies are to be dimensioned so that (for the samenumber of strokes per unit of time for the individual stages) the inletcylinder volume of a stage in consideration substantially equals theoutlet cylinder volume of the previous stage. Accordingly, in some ofthe embodiments the cubic capacity of the piston-cylinder assemblies inseries is progressively reduced. In reality the above assumption—becauseof the aforementioned effects—does not apply precisely but onlyapproximately (see German “Dubbel” mechanical engineering text book,17^(th) Edition, published by Springer-Verlag, 1990, pages P30-P31),that the cubic capacity is progressively reduced from stage to stagebasically holds, however.

In some of these embodiments progressively reducing the cubic capacityis achieved by the piston-cylinder assemblies—having the same strokebecause of their assignment to one and the same wobble plate—assigned toa wobble plate comprising a progressively reduced diameter.

Other embodiments incorporate two wobble plates in which, for example,first the piston-cylinder assemblies of the first wobble plate and thenthe piston-cylinder assemblies of the second wobble plate are connectedin series with a progressively reduced cubic capacity. In some of theseembodiments progressively reducing the cubic capacity extends over thewobble plates by reducing the cylinder diameter; i.e. thepiston-cylinder assembly of the second wobble plate first in flow has asmaller diameter that the piston-cylinder assembly of the first wobbleplate last in flow.

Since in a wobble plate compressor the cylinder stroke is definedrelative to the axis of rotation due to the inclination of the wobbleplate, a smaller cubic capacity is achievable also by a lesser slant ofthe wobble plate. In some of these embodiments the second wobble plateis arranged less slanted than the first wobble plate to achieve thereduction in cubic capacity.

In some of these embodiments both means of reducing the cubic capacityare also combined with each other, i.e. the second wobble plate isarranged less slanting than the first wobble plate to reduce the stroke,and in addition the first piston-cylinder assembly of the second wobbleplate features a smaller diameter than that of the last piston-cylinderassembly of the first wobble plate.

In some of the multistage embodiments the compressor stages aredimensioned for the multistage increase in pressure so that—e.g.starting with atmospheric pressure (1 bar)—an increase in pressure to atleast 200 bar, in other embodiments to even at least 400 bar, isachieved. The compressor is thus particularly useful for compressinggases which at room temperature practically defy liquifying, such ashydrogen, nitrogen, oxygen, air, rare gases and especially natural gas(mainly methane).

In a compressor a sudden drop in gas pressure in the cylinder occurs dueto the typically sudden opening of the outlet valve when maximumcompression is attained in a cylinder, resulting in a shock moment aboutthe drive axis (i.e. the longitudinal centerline) of the compressorwhere a wobble plate compressor is concerned. As already mentionedabove, in some embodiments two wobble plates are provided, each of whichis powered by a drive shaft stub counter rotatively, whereby the twodrive shaft stubs are arranged coaxial, for instance. In some of theseembodiments the two counter rotating wobble plates are intercoupled insuch an angular relationship that outlet timing of cylinders formingsuch cylinder pairs coincide in each case. For example, the outlettiming of the first and third stage and that of the second and fourthstage coincide. Because of this synchronism and the counter rotation ofthe two drive shaft stubs the shock moments occur substantialsimultaneously and are opposite in sign, so that in this arrangement thecited shock moments are compensated at least in part.

The assembly mentioned above of two counter rotatively powered wobbleplates has the effect of reducing the shock also in wobble platecompressors other than the multistage type, e.g. in compressors in whichthe plurality of piston-cylinder assemblies belonging to a stage isconnected in parallel, or in which a plurality of independent gas flowsfrom the individual cylinder is compensated in a single-stage, forexample, for application in air-conditioning compressors or the like.The cylinder diameters and strokes of the individual piston-cylinderassemblies are more or less the same in such single-stage embodiments.Although the instant claim 1 is directed at a multistage compressor, thepresent application docs thus disclose also in general a wobble platecompressor with counter rotatively powered wobble plates irrespective ofthe compressor configured multistage or single-stage. The applicant thusreserves the right to direct an independent claim at an assembly withtwo counter rotatively powered wobble plates which does not require thatthe wobble plate compressor is a multistage compressor. Such anindependent claim would read e.g. a wobble plate compressor comprisingtwo wobble plates each assigned at least two piston-cylinder assemblies,each of the two wobble plates being powered by a drive shaft stub, thetwo drive shaft stubs being arranged coaxial and counter rotatively. Thefeatures of the current claim 1, of the remaining claims and of thedescription/drawing can as dependent claims relating back to thisindependent claim.

In some of the embodiments having counter rotatively powered wobbleplates a bevelled drive gear is mounted at each inner end of the driveshaft stub, between which a bevel pinion is arranged for powering bothwobble plates simultaneously counter rotatively.

In some of the embodiments the wobble plates themselves arenon-rotatable, they being controlled by a rotatable wobble membersimilar to the assembly as it reads from the aforementioned U.S. Pat.No. 4,008,005, for instance. In such an assembly the con rods of thecylinder are exposed to no bearing or friction forces produced by theactual rotation, but merely to bearing or friction forces due to thewobble motion.

In some embodiments the con rod does not directly engage the piston (asis usual in prior art). Instead, in these embodiments a piston guide rodis disposed between con rod and piston, suitable guided e.g. in alocating hole machined in an inside cover. The piston guide rod preventstransverse forces being transmitted from the con rod to the piston whichwhen the wobble plate is stationary are in any case only slight.

In some embodiments some or all of the bearings between relativelyrotatable parts are angular contact roller bearings which due to theirangular location are suitable for absorbing axial forces. For exampleone or more of the following bearings is/are configured as angularcontact roller bearings: (i) bearing of a non-rotatable wobble platerelative to a rotatable wobble plate (in embodiments with anon-rotatable wobble plate); (ii) bearing of a rotatable wobble plate(in embodiments with a rotatable wobble plate) or a rotatable wobblemember (in embodiments with a rotatable wobble member) relative to acasing; and (iii) bearing of a drive shaft stub relative to a casing (inembodiments with drive shaft stubs). In some embodiments the angularcontact roller bearings are relative to needle bearings at an angle tothe axis of rotation, in others the bearings involved have angledrollers so that even without angular location of the roller axes theyare capable of absorbing axial forces, such as bevelled roller bearingsand barrelled bearings (also combinations thereof in which e.g. somebearings are angular needle bearings, other and bevelled roller bearingsexist). In some embodiments the bearings supporting the drive shaft oreach drive shaft stub are two angular contact roller bearings facingaway from each other. In some embodiments both the wobble member or thewobble plate and the drive shaft stub run in angular contact rollerbearings in the casing, and the wobble member or wobble plate and thedrive shaft stub are axial shiftingly (but non-rotatable) connected toeach other so that wobble member or wobble plate and drive shaft stubare decoupled from each other as regards the axial forces. The angularcontact roller bearings mounting the wobble plate in the wobble memberand those of the wobble plate member in the casing are speciallysuitable to absorb the axial and radial components of the forcesoccuring on actuation of the pistons.

One problem as known with compressors is that lubricants can evaporatefrom the cylinder walls into the gas being compressed. In addition tothis, at high compressor temperatures the lubricant may be decomposed.This is why in some embodiments the pistons and/or the walls of thecylinders are lined at least in part with anti-friction plastics, suchas e.g. polytetrafluroethylene (PTFE). For the pistons PTFE piston ringsmay be involved, for example, and as regards the cylinder wall cylindershells. Such anti-friction linings permit doing away altogether withlubrication of the pistons in the cylinder by liquid lubricants (e.g.oil) in some embodiments, or at least to reduce the amount of lubricantneeded.

Some embodiments relate to methods in which a wobble plate compressor ofthe kind as described presently is used to compress gases which at roomtemperature practically defy liquifying, such as hydrogen, nitrogen,oxygen, air, rare gases and/or natural gas to a pressure of at least 200bar, preferably to at least 400 bar. One particularly suitable useinvolves the compression of natural gas (mainly methane) for fuellingvehicles operated on compressed natural gas (CNG).

Referring now to FIGS. 1 and 2 there is illustrated partly inlongitudinal section an example embodiment of a dual wobble platecompressor 101, i.e. a wobble plate compressor with two wobble plateassemblies 102, 103, FIG. 2 showing substantially just one of the twowobble plate assemblies, namely 103.

The two wobble plate assemblies 102, 103 are accommodated facing eachother at the drive end in a substantially tubular casing identified as awhole by 006 and assembled from a plurality of parts.

Running through the casing 006 central and at right angles to itslongitudinal centerline mounting two drive shaft stubs 009 is a maindrive shaft. Of the two drive shaft stubs 009 only one is shownidentified as such, the same as the many parts of the two wobble plateassemblies 102, 103 which are identified just for one or other wobbleplate assembly, since the parts for both are provided similar oridentical, albeit mirror-inverse to each other. Mounted at the outer end(relative to the casing 006) of the main drive shaft is a drive flangefor connecting a drive means by means of a nut 005 and a splined joint.Inserted in the wall of the casing 006, configured flat in this case, isa bearing mount 002 mounting two angular contact roller bearings 003,004. Seated at the inner end of the main drive shaft is a bevel pinion001.

The bevel pinion 001 engages two bevel gears 007. These are seated on aflange 008 bolted in each case to the drive shaft stubs 009. The driveshaft stubs 009 each run in two angular contact roller bearings 011, 012secured in a cylindrical bearing support 010 bolted to a cross platepenetrating the casing 006.

Seated at the other side of this cross plate is a bearing base 013supporting a rotating wobble member 015 via an angular contact rollerbearing 014. In this arrangement the middle of the bearing base 013 isrecessed to permit the end of the drive shaft stubs 009 facing away fromthe bevel gears 007 to pass through without contact, to which the wobblemember 015 is splined and secured in place by a fastener nut.

Mounted on the free outboard flange of the wobble member 015 orientedslanting to the longitudinal centerline of the drive shaft stub 009 is afurther angular contact roller bearing 016 supported by a non-rotatablewobble plate 017 which in turn is supported by a bevel toothing 018 anda middle ball 019 on a fixed part 020. The fixed part 020 is securedbetween two walls 021 which in turn are bolted to a crosswall.

The bevel toothing 018 permits the wobble plate 017 to follow the wobblemotion of the wobble member 015 without being included in its rotation,since one part of the bevel toothing 018 is stationary and is thusnon-rotatable, resulting in the wobble plate 017 also being unable torotate because of the mesh, whilst the ball 019 permits the pivotingmotion.

At the side of the wobble plate 017 facing away from the wobble member015 two spherical recesses are sited radially opposed and equally spacedaway from the center point of the ball 019, the recesses being coveredby a cover 022. The cover 022 comprises a hole in the middle, i.e. isconfigured just as a rim and is likewise spherically hollowed aroundthis hole.

Inserted in the recesses is the spherical end of a con rod 023 which isheld by the cover 022. The con rod 023 ends also at the other side in aball. This other ball is located in a similar spherical recess coveredby a cover 024 and which is configured in the end of a piston rod 025 ineach case which in turn is guided in a locating hole 036 orientedparallel to the drive shaft stub 009. The locating holes 036 areconfigured in the aforementioned crosswall and coated withpolytetrafluoroethylene (PTFE) or the like to obtain a totally linearmotion of the piston rods 025 without resulting in any substantialfriction being produced thereon.

Rotation of the bevel pinion 001 results in rotation of the two wobblemembers 015 at the same speed, but counter rotatively, producingreciprocation of the piston rods 025: the two in-line piston rods 025shown at the top in the drawing move towards each other in the samesense, but in opposite sense to the likewise in-line piston rods 025moving towards each other in the same sense as shown at the bottom inthe drawing.

The spherical ends of the con rods 023 and/or the recesses seating themare coated to reduce friction, for instance with PTFE and run, like thepiston rods, dry in operation. The ball 019 and/or the sections of thebevel toothing 018 seating it are also coated to reduce friction, forinstance with PTFE as is the case in some embodiments also with thebevel toothing 018 and with the bevel drive 001/007. The angular contactroller bearings require no lubrication, they being sealed for life sothat the dual wobble plate compressor 101 runs dry in operation. Inother embodiments, however, at least the middle part of the casing withthe bevel drive 001/007 and the angular contact roller bearings 011, 012are provided with grease lubrication or with an oil sump whichlubricates through the bearing 014 also the remainder of the wobbleplate compressor as described hitherto. On the far side of the locatinghole 036 the following parts in the embodiment as shown run dry.

The piston-cylinder assemblies 026, 031; 027, 032; 039, 033; 038, 034form in this sequence of the reference numerals the first, second, thirdand fourth compression stage, they for this purpose being connected inseries in the gas flow and comprise from stage to stage a progressivelyreduced cubic capacity. This reduction in cubic capacity is achieved inthe embodiment as shown by a reduction in the cylinder diameter fromstage to stage and in addition by a reduced stroke in the third andfourth stage as compared to that of the first and second stage.

The pistons 026, 027, 038, 039 are powered by the piston rods 025 towhich they are fastened by means of a nut 035, 045, 046. The pistons026, 027, 038, 039 feature piston rings of PTFE or the like. In someembodiments—in addition thereto or as an alternative—the inner surfacesof the cylinders 031, 032, 033, 034 are coated with PTFE or the like.

The cylinders 031, 032, 033, 034 are each formed by two tubular sectionslocated in a crosswall (comprising the locating holes 036). Thecrosswall stands crosswise on a base plate 042. The two each tubularsections are interconnected or connected to the crosswall by connectingflanges 029, 030, 041, 042 to form a full-length cylinder 031, 032, 033,034 and to secure the cylinder to the crosswall. At the outer end thecylinders 031, 032 of the first and second stage (i.e. the right-handcylinders) and the cylinders 033, 034 of the third and fourth stage(i.e. the left-hand cylinders) are closed off from the outside by eachcover 028, 040 seating valves having a free valve cross-section which isprogressively reduced from stage to stage. Provided furthermore frontingthe cover 028, 040 in each case is a cylinder end flange 047, 048receiving in common the ends of the two right-hand cylinders 031, 032and left-hand cylinders 033, 034 respectively. In the embodiment asshown the valves are gas-controlled valves, e.g. combined pressureopening/check valves opening in the inlet direction so that on theinwards stroke gas flows in each of the cylinders and which in theoutlet direction do not open until a certain pressure (progressivelyincreasing from stage to stage) is attained typically just before theouter dead center. In other embodiments separate inlet and outlet valvesare provided. In some embodiments the valves are not controlled by thegas flow but mechanically by a valve control mechanism which derives itsmotion from the rotation of the wobble plate drive.

Porting into each cover 028, 040 are two pipes 049, 050 and 051, 052respectively. In an external pipe connecting system these pipes areinterconnected as well as to a low-pressure gas input and ahigh-pressure gas outlet so that the gas flows from the low-pressure gasinput to the first stage, from there to the second stage and so on infinally flowing from the fourth stage to the high-pressure gas outlet.In embodiments having valves and pipe sections used in common for theinlet and outlet, directional control valves (e.g. gas controlleddirectional control valves of the check valve type) ensure that the gasflow takes a different path depending on the direction concerned (forinstance, when inlet in the second stage, the path from the first stageto the second stage, whereas when outlet from the second stage, the pathfrom the second stage to the third stage). In embodiments with separatevalves and pipes for the inlet and outlet, no such directional controlvalves are provided; instead, the pipe from the input through theindividual stages to the output is guided as a single loop. In someembodiments the pipes between the stages and leading to the output arecooled for a better intercooling of the gas to be compressed.

In the position as shown in FIG. 1 all pistons 026, 027, 038, 039 are atone of their two dead centers, namely pistons 026, 039 of the first andthird stage are at their inner dead center and the pistons 027, 038 ofthe second and fourth stage at their outer dead center. Assigning anangle of 360° to a full reciprocation of a piston, the difference in theangle between the pistons of stages in sequence is thus 180° in eachcase, resulting in a favorable gas flow through the various stages;although, of course, the relatively positions of the cylinders can alsobe selected otherwise.

As evident from FIG. 1 the wobble plate 017 of the third and fourthstage is oriented less slanting to the drive axis (e.g. the shaft stub009) than the wobble plate 017 of the first and second stage. This isachieved by shaping the wobble members 015 correspondingly differingly,i.e. the difference in length of the legs in the section view of thewobble members 015 as shown in FIG. 1 for the wobble member 015 of thethird and fourth stage is less than that of the first and second stage.In accordance with the different slant of the wobble plates 017 thestroke of the pistons 039, 038 of the third and fourth stage is lessthan that of the pistons 039, 038 of the first and second stage.Correspondingly also the cylinders 033, 034 of the third and fourthstage shorter than the cylinders 031, 032 of the first and second stage.

This compressor with its two wobble plates as shown is mounted as awhole in a casing which due to the crosswalls and covers is particularlytorsionally rigid, despite its length. Although the substantial part ofthe compressors runs dry, there is no corrosion of the PTFE coatedsurfaces even when temperatures are attained at which lube oil wouldalready be decomposed.

With this simple, small multistage compressor (low friction when PTFEcoated) gases can be compressed to pressures in the range 200 to 400bar. Referring now to FIG. 3 there is illustrated by way of example howthe wobble plate compressor 101 as shown in FIGS. 1 and 2 is used forcompressing natural gas in fuelling a natural gas powered vehicle 114.Natural gas is supplied to a filling station 110 via a low pressuresupply line 111. This may involve e.g. a final supply line of a naturalgas distribution grid in which a slight overpressure of 0.1 bar usuallyexists. As an alternative it is also possible to connect such a CNGfilling station 110 to a supply line which, for achieving a higherdelivery capacity, features a higher delivery pressure which maytypically amount to an overpressure of approximately 2.5 bar in theexample as shown in FIG. 3. A dual wobble plate compressor 101 of thekind as described above, compresses the low pressure natural gas by itsfour stages of progressively reduced cubic capacity to a high (absolute)pressure, e.g. of 200 bar. The high pressure natural gas flows via thehigh-pressure line 112 to a CNG interface 113 to which a CNG tank 115 ofthe vehicle 114 can be connected pressure tight for fuelling withcompressed natural gas.

The embodiments described thus provide an improved high pressurecompressor which e.g. is suitable for equipping CNG filling stations.

All publications and existing systems cited in this description areincorporated therein by referencing.

Although certain products and methods built in agreement with theteaching of the invention have been described, the scope of protectionafforded by this patent is not restricted thereto. On the contrary, thepatent covers all embodiments of the teaching of the invention readingliterally or by the equivalence doctrine from the scope of protection asclaimed.

1. A wobble plate compressor comprising at least one wobble plateassociated with at least two piston-cylinder assemblies, wherein thewobble plate compressor forms a multistage compressor in which thepiston-cylinder assemblies are connected in series in the flow and thecubic capacity of the piston-cylinder assemblies is progressivelyreduced in series.
 2. The wobble plate compressor as set forth in claim1 wherein the piston-cylinder assemblies associated with a wobble platecomprise a progressively reduced diameter to achieve a progressivelyreduced cubic capacity.
 3. The wobble plate compressor as set forth inclaim 1 comprising at least two wobble plates each associated withpiston-cylinder assemblies wherein to progressively reduce the cubiccapacity, the piston-cylinder assembly first in the flow of the wobbleplate comprises a smaller diameter than the piston-cylinder assemblylast in flow of the first wobble plate.
 4. The wobble plate compressoras set forth in claim 1 comprising at least two wobble plates eachassociated with piston-cylinder assemblies wherein to progressivelyreduce the cubic capacity the second wobble plate is arranged less skewthan the first wobble plate.
 5. The wobble plate compressor as set forthin claim 1 wherein the individual compressor stages are dimensioned fora multistage increase in pressure of the gas to be compressed to atleast 200 bar.
 6. The wobble plate compressor as set forth in any of theclaim 1 comprising two wobble plates each powered by a drive shaft stub,the drive shaft stubs being arranged coaxial and counter rotatively. 7.The wobble plate compressor as set forth in claim 6 wherein the innerend of the drive shaft stubs seats in each case a bevel gear betweenwhich a bevel pinion is disposed for simultaneously, counter rotativelydrive of both wobble plates.
 8. The wobble plate compressor as set forthin claim 1 wherein the wobble plates are non-rotatable and arecontrolled by a rotatable wobble member.
 9. The wobble plate compressoras set forth in claim 1 comprising bearings disposed between relativelyrotatable parts, at least one of the following bearings being configuredas an angular contact roller bearing: (i) bearing of a non-rotatablewobble plate relative to a rotatable wobble member; (ii) bearing of arotatable wobble member relative to a casing; and (iii) bearing of adrive shaft stub relative to a casing.
 10. The wobble plate compressoras set forth in claim 1 wherein the pistons and/or the walls of thecylinders are lined at least in part with anti-friction plastics.
 11. Awobble plate compressor comprising at least one pair of wobble plates,each wobble plate associated with at least one piston-cylinder assembly,each wobble plate of the pair powered by a drive shaft stub, the driveshaft stub being arranged coaxial and counter rotatively.
 12. A methodin which a wobble plate compressor as set forth in claim 1 is used forcompressing natural gas to a pressure of at least 200 bar.